A. Technical Field
The present invention relates generally to optical communication network systems, and more particularly, to the routing of information within an optical communication system, having both digital and optical express-thru nodes, to ensure path diversity and effective load balancing across the network.
B. Background of the Invention
Optical communication network system may include different types of network elements and nodes. For example, certain optical networks may include both digital nodes and optical-express nodes. Each of the digital nodes has lambda switching capability that enables a digital node to switch wavelengths from one port to another other port. This routing operation requires that a wavelength be converted into the electrical domain, processed, internally routed to a particular port and converted back to the optical domain.
Optical-express nodes do not process optical data within the electrical domain; rather, an optical wavelength(s) is optically transmitted through the node and not terminated in the data plane at the node. For example, an optical-express node may have two ports that are coupled directly to each other by a piece of optical fiber that effectively causes the data plane to bypasses the electrical domain at the particular node. One skilled in the art will recognize that there may be other structures within an optical-express node that allows an optical wavelength(s) to be transmitted through the node within the optical domain.
The location and types of nodes may vary within a network. These nodes may be connected directly or there can be one or more optical amplifiers between them. Two nodes that are not physically adjacent may behave like virtually adjacent neighbors (referred to as “virtual digital neighbors”) and maintain virtual connections in which an optical node express-thru node effectively optically forwards traffic within the connection. It is oftentimes a requirement that these digital nodes identify their virtual neighbors when they are not physically adjacent.
Typically, network neighbors (whether digital or optical) are discovered by using a discovery protocol, such as the “HELLO” protocol which is commonly known within the art. This protocol is responsible for establishing and maintaining neighbor relationships and ensuring bidirectional communication between neighboring networks elements.
‘Hello’ packets are sent to all router interfaces at fixed intervals. When a router sees itself listed in its neighbor's “Hello” packet, it establishes a bidirectional communication. An attempt is always made to establish adjacencies over point-to-point links so that the neighbors' topological databases may be synchronized. However, the traffic engineering topology view of a generalized multi-protocol label-switching (“GMPLS”) network provides a data-plane connectivity view of the network, which is represented at an appropriate layer of switching/connectivity capability. This traffic engineering topology gives a view of only digital nodes and not optical express-thru node or optical amplifiers. Thus, it may differ from the physical topology of the network when the digital nodes are not physically adjacent and have optical amplifiers or optical express-thru nodes in between.
It is important that a complete topology be established of the network including both digital nodes and optical express-thru nodes. This complete topology allows for more efficient routing of data through the network and enables a more accurate establishment of link diversity, load balancing and link count across the network.
A failure to provide link diversity within the network lowers the redundancy of the network system and increases its susceptibility to losing large amounts of data if a node was to go down or a piece of fiber was cut. For example, a shared link between a network path and its corresponding redundant path is undesirable because a failure occurring on the shared link could be potentially be fatal to traffic on the path because both the primary and redundant paths are disabled.
A failure to accurately balance traffic through the network may result in bottlenecks that can significantly reduce the performance of the network. An inaccurate link count for the network may result in inefficient overall management of the network because network operations are being based on an incomplete network topology model.